During the operation of combustion engines the quality of the combustion events depends on various conditions. One condition is how well the fuel is mixed with air in the combustion chamber. A poor air fuel mix may yield unwanted soot, and/or hydrocarbon emissions. This may be, in particular, during cold starts. One contributing factor to poor mixing is fuel impingement onto the top surface of surface of the piston as it moves within the combustion chamber. Long spray penetration, may result in the spray hitting the top surface of the piston, which may tend to keep the fuel at a cooler, liquefied, state. Fuel injectors have been used to inject fuel at high velocity in an attempt to atomize the fuel. Still, impingement onto the surface of the piston may still occur.
U.S. Pat. No. 7,458,364 to Allen discloses a fuel injection system wherein an attempt is made to improve atomization. The '364 disclosure includes a so called mixing chamber into which a positive displacement pump injects a measured amount of fuel. An air, or exhaust gas, conduit provides a gaseous make-up volume to the mixing chamber as a partial vacuum is produced in the adjacent combustion chamber to pull exhaust gas and fuel into the combustion chamber in a combined stream in an attempt to entrain the fuel into the exhaust stream. The vacuum is created in the combustion chamber by delaying the opening of an inlet valve as the piston starts a downward stroke. The mixing chamber includes an atomizing nozzle at an outlet side thereof, to accelerate the flow.
This approach has a number of shortcomings. For one, the '364 system requires a very particular operation of the charge air inlet valve in order to create a vacuum in the combustion chamber to cause air or exhaust to flow through the mixing chamber to entrain the fuel. The '364 design is intended to be used with smaller single cylinder engines that do not include a fuel pump. The positive displacement pump is designed for metered injection, not for increased pressure. In addition, there appears to be a relatively short time during which the fuel is exposed to the passing air or exhaust flow. There also appears to be little time for any appreciable heat transfer between the fuel and exhaust. The stream of exhaust and stream of fuel appear to be merely blended. It appears the fuel only becomes atomized as it passes from the atomizing nozzle into the combustion chamber within the blend.
The inventors herein disclose an engine, a fuel injector, and a method of injecting fuel into a combustion chamber of the engine that reduces the likelihood of impingement of the injected fuel onto the top surface of the piston, and provides an improved air-fuel mixture.
Embodiments may provide a fuel injector including an injector body defining a cavity on an inside thereof and an outside surface. The injector body may have a central axis. One or more passages may pass from an inlet at the cavity through the outside surface. Each of the one or more passages may have a first inner contour forming a first angle with the injector body central axis, and a second inner contour forming a second angle with the injector body central axis. An injector pin may define a fuel pass-though volume movable within the cavity to selectively overlap an outlet of the pass-through volume with inlet of the one or more passages to selectively direct fuel in varying quantities along one or both of the first inner contour and the second inner contour. In this way, at or during, for example, an early segment of a compression stroke, when the piston may be low, and relatively far from the injector, the injected spray may have a relatively deep penetration angle; and also in this way at or during, for example, a late segment of the compression stroke, when the piston may be high, and relatively close to the injector, the injected spray may have a shallow, or zero, penetration angle.
In some examples a high pressure fuel may be delivered from a high pressure reservoir and/or fuel pump or the like, to the injector nozzle(s) through an internal fuel passage inside the injector body. The pressurized fuel may pass through one or more pass-through volumes. The fuel may pass through a fuel conjunction volume and/or one or more fuel side volumes. The fuel side volumes, or pass-through volumes, may be positioned to face or overlap injector nozzles. Each nozzle may have, for example, an annulus inlet and a circular outlet with a solid cone inside and mounted by, for example, four support legs. The inlet annulus area may be equal to the circular outlet area. The ratio of the outlet diameter d1 to inlet diameter d2 may be used to control the range of the injection spray angle. In this way, an amount of overlap may be selectively controlled by, for example, an engine controller in accordance with piston position, and, in this way, may vary an amount of spray penetration.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.